Pneumatic conveyor duct branch connection fitting



July 18, I w. E. CROSS, JR

PNEUMATIC CONVEYOR DUCT BRANCH CONNECTION FITTING Filed March 15, 1965 INVENTOR WILE'Y E. CROSS JR.

United States Patent 3,331,639 PNEUMATIC CONVEYOR DUCT BRANCH CONNECTION FITTING Wiley E. Cross, Jr., Glen Allen, Va., assignor to Vol-:es Limited, Guildford, Surrey, England Filed Mar. 15, 1965, Ser. No. 439,671 Claims. (Cl. 302-28) This invention concerns improvements in pneumatic conveyor ducts of the kind used in connection with the automatic distribution of tobacco from a feed-in station to a number of separate utilising points.

It is known to employ ducts which are selectively influenced by suction to induct a tobacco-feed. Some systems employ separate ducts for each utilising point, but this is expensive and it is generally preferred to use a single main duct from which subsidiary ducts are branched or manifolded.

A common trouble in the use of branched ducts is the formation of blockages of tobacco at the position of the branch when conveying suction is stopped and an inadvertent momentary reverse air flow returns the tobacco towards the feed-in station.

According to the invention I provide in a pneumatic tobacco feed system having ducts led from a feeding station to a number of utilising points, which ducts are selectively influenced by suction induced by a fan, a branch connection fitting dividing one duct into two, said branch connection fitting including a cranked leg of sufiicient volumetric capacity to contain tobacco returned on inadvertent reverse flow on cessation of suction in the branch duct.

In preferred forms of the invention the branch connection has a side wall (joining a side wall of the duct being divided) at an angle not greater than 170.

The branch connection fitting may conveniently be arranged so that the outlet portion of the fitting to be connected to the branched duct is arranged substanially parallel to the duct from which it divides.

In any case it is found effective to form the branch connection portion of the fitting with a radiused wall downstream from the feed-in station and opposite to a plane wall, these two walls constituting opposite sides of the cranked leg.

The above and other features of the invention are embodied in one preferred form of branch connection fitting which will now be described as an example with reference to the accompanying drawings in which:

FIGURE 1 is a side view of a complete connection including a fitting according to the invention.

FIGURE 2 is a view in the direction of the arrow A in FIGURE 1.

The illustrated fitting is intended to be used in a conveying system having a delivery duct, a number of branch ducts and a return duct, as for example the system described in applicants US. Pat. 3,174,805. A plurality of fittings as disclosed in the drawing of this application are connected at 1 and 2 in series in the delivery duct and branch outlets 3 connect in parallel to separate discharge stations in the branch ducts and to the return duct. Air flow is obtained with a suction fan at the end of the return duct. Flow through the individual parallel branch ducts is determined by means of a conventional butterfly valve and a check valve in each of the parallel branches at each of the discharge stations. In operation the branches are normally opened one at a time. When r 3,331,539 Ice Patented July 1 1967 changing from a branch at some distance from the delivery duct inlet to one nearer the inlet some of the material conveyed remains in the delivery duct between the two branches. This material is returned to the fitting and delivered through the now open branch because of a controlled leakage at the far end of the delivery pipe. The branch connection fitting comprises a single circular main duct 1 divided into two subsidiary ducts 2 and 3 of commensurate cross-section and has a cranked or dogleg offshoot from the side Wall 4 of a square sectioned extension of the main duct.

The main duct continues (as the subsidiary duct 2) from the direction of the input station in a straight line from the junction position and the other subsidiary duct 3 lies parallel to it.

The rear wall 5 of the branch connection (that is to say the wall nearest the feed-in station) is plane and defines an angle of about with the main duct wall 4. The opposite wall 6 is substantially semi-circular presenting a smooth rounded contour to the tobacco inlet.

The remaining two walls 7 and 8 of the branch connection, which may be formed as extensions from the main duct walls, are plane and the wall 7 constitutes a hinged sight door with clip 9.

Appropriate lengths for the branch connection walls may be determined empirically according to the duct cross-sections and the duty conditions of the tobacco supply system, the important consideration being that the cranked portion enclosed between walls 5, 6, 7 and 8 must have suficient volumetric capacity to contain such quantity of tobacco as is returned down the duct 3 upon cessation of suction in the branch to which it is connected.

Experimental designs show that satisfactory operation is possible with a wide range of angle between the branch rear wall and the main duct wall up to about Under certain conditions an angle less than a right angle may be found suitable, in which case the rear wall actually slopes back towards the tobacco inlet and a pocket or sump for returned tobacco is formed.

I claim:

1. In a pneumatic tobacco feed system of the type including a delivery duct and a return duct connected to a suction fan, the delivery duct being branched to each of several discharge stations, the improvement comprising a branch duct fitting having an inlet and first and second outlets said inlet and first outlet being formed as aligned duct portions for insertion in and continuation of the delivery duct, the second outlet being for connection to a discharger in a branch and formed as a cranked leg connected to said inlet by one wall joining a wall of the inlet duct portion at an angle not greater than 170 and an opposed curvilinear wall facing the inlet and marrying adjacent walls of both outlets to present a smooth contour therebetween.

2. In a pneumatic tobacco feed system a branch duct fitting according to claim 1 wherein said aligned duct portions include an intermediate duct portion having planar walls, said angled and opposed curvilinear walls of the cranked leg joining one of said planar walls to border an opening therein, said cranked leg being a duct completed by another pair of opposed Walls which are coplanar with and extensions of the pair of planar walls adjacent said one planar Wall.

3. In a pneumatic tobacco feed system a branch duct fitting according to claim 2 wherein one of said pair of planar walls is provided with a hinged sight door.

4. In a pneumatic tobacco feed system a branch duct 'fitting according to claim 1 wherein said second outlet terminates in a duct portion for connection to a .branch duct and which is parallel to and positioned at one side of the aligned duct portion of said first outlet. 3 r

5. In a pneumatic tobacco feed system a branch duct fitting according to claim 1 wherein said angled wall of the crank leg is disposed at approximately 135 to the wall of the inlet to which it is joined.

4 References Cited UNITED STATES PATENTS 3,106,427 10/1963 Mortimer 30228 3,174,805 3/1965 Mortimer 302-28 FOREIGN PATENTS 413,219 7/1934 Great Britain. 

1. IN A PNEUMATIC TOBACCO FEED SYSTEM OF THE TYPE INCLUDING A DELIVERY DUCT AND A RETURN DUCT CONNECTED TO A SUCTION FAN, THE DELIVERY DUCT BEING BRANCHED TO EACH OF SEVERAL DISCHARGE STATIONS, THE IMPROVEMENT COMPRISING A BRANCH DUCT FITTING HAIVNG AN INLET AND FIRST AND SECOND OUTLETS SAID INLET AND FIRST OUTLET BEING FORMED AS ALIGNED DUCT PORTIONS FOR INSERTION IN AND CONTINUATION OF THE DELIVERY DUCT, THE SECOND OUTLET BEING FOR CONNECTION TO 